Production of plastic foams, preferably rigid foams containing urethane groups or urethane and isocyanurate groups, and blowing agent-containing emulsions for this purpose

ABSTRACT

A process for the production of plastic foams, preferably rigid foams containing urethane groups or urethane and isocyanurate groups, by reacting 
     a) an organic and/or modified organic polyisocyanate with 
     b) at least one relatively high-molecular-weight compound containing at least two reactive hydrogen atoms, and, if desired, 
     c) a low-molecular-weight chain extender and/or crosslinking agent, 
     in the presence of 
     d) a blowing agent, 
     e) a catalyst and, if desired, 
     f) assistants and/or additives, 
     in which the blowing agent (d) used is at least one vinylfluoroalkane of the formula CH 2  ═CH--C n  F 2n+1  in which n is an integer from 1 to 6, (di), or a mixture of at least one such vinylfluoroalkane (di) and at least one further physical and/or chemical blowing agent (dii) which is different from (di), blowing agent-containing emulsions which contain at least one vinylfluoroalkane and at least one starting component (a), (b), (c) or (b) and (c) and said plastic foams containing at least one vinylfluoroalkane as insulating gas.

The present invention relates to a process for the production of plasticfoams, preferably rigid foams containing urethane groups or urethane andisocyanurate groups, by reacting the starting components (a), (b) and,if desired, (c), where the blowing agent employed is at least onevinylfluoroalkane of the formula

    CH.sub.2 ═CH--C.sub.n F.sub.2n+1

in which n is an integer from 1 to 6, (di), or a mixture comprising atleast one such vinylfluoroalkane (di) and at least one further physicaland/or chemical blowing agent (dii) which is different from (di), and toblowing agent-containing emulsions which contain at least onevinylfluoroalkane (di) or a mixture of (di) with at least one otherblowing agent (dii) and at least one of the starting components (a), (b)or (c) or (b) and (c), and to plastic foams containing saidvinylfluoroalkane as insulating gases.

Chlorofluorocarbons (CFCs) such as fluorotrichloromethane (CFC 11),dichlorodifluoromethane (CFC 12) and1,1,2-trichloro-1,2,2-trifluoroethane (CFC 113) are at present theblowing agents and insulating gases most widely employed for themanufacture of all kinds of plastic foams intended for insulation, inparticular closed-cell foams, especially polyurethane orpolyisocyanurate foams, extruded polystyrene and polyethylene foams,phenolic foams, poly(vinyl chloride) foams, etc.

CFCs 11 and 12 are also employed for the manufacture of polyolefin foamssuch as polyethylene and polypropylene, polystyrene or poly(vinylchloride), more especially intended for packaging.

However, CFCs 11, 12 and 113 are included amongst fully halogenatedchlorofluorocarbons which, because of their high chemical stability, aresuspected of attacking or degrading stratospheric ozone and whose use isenvisaged to be prohibited at the end of this century.

As a solution to this problem it is currently envisaged to replace theCFCs by chlorofluorohydrocarbons containing at least one hydrogen atom,such as chlorodifluoromethane (HCFC 22),1,1-dichloro-2,2,2-trifluoroethane (HCFC 123),1-chloro-1,2,2,2-tetrafluoroethane (HCFC 124),1,1-dichloro-1-fluoroethane (HCFC 241b) and 1-chloro-1,1-difluoroethane(HCFC 142b). Although the HCFCs exhibit ozone-depletion potentials(O.D.P.) which are markedly lower than those of the CFCs, their O.D.P.is nevertheless not zero and their substitution for the CFCs cantherefore represent only a temporary solution.

There is therefore still a need for compounds which have no destructiveeffect on stratospheric ozone (O.D.P.=0) and exhibit properties whichare similar to those of CFCs 11, 12 and 113, in order to replace thelatter as blowing agents and insulating gases in the manufacture ofplastic foams.

It has now been found that this problem can be solved by employingvinylfluoroalkane of formula:

    CH.sub.2 ═CH--C.sub.n F.sub.2n+1

in which C_(n) F_(2n+1) denotes a linear or branched perfluoroalkylradical and n is an integer from 1 to 6. These compounds have ODP ofzero; the properties of the preferred compounds are illustrated by thefollowing table.

    ______________________________________                                                      C.sub.n F.sub.2n+1                                              PROPERTIES      (CF.sub.3).sub.2 CF                                                                      C.sub.4 F.sub.9                                                                        C.sub.5 F.sub.13                          ______________________________________                                        Boiling point (°C.)                                                                    31         59       105                                       Vapour thermal conduc-                                                                        9.2        8.1      5.7                                       tivity at 10° C. (mW/m K)                                              Vapour pressure at 10° C.                                                              445        137      143                                       (mbar)                                                                        ______________________________________                                    

The present invention therefore relates to the use of at least one ofsaid vinylfluoroalkanes as blowing agent and insulating gas in theproduction of plastic foams.

The vinylfluoroalkane of formula CH₂ 50 CH--C_(n) F_(2n+1) can beobtained industrially by processes which are known per se, for exampleby a two-stage process consisting successively in:

the addition of ethylene to the corresponding perfluoroalkyl iodideC_(n) f_(2n+1) in the presence of a catalyst based on copper andethanolamine, and

the dehydroiodination of the iodide C_(n) F_(2n+1) --CH₂ CH₂ I thusobtained, in the presence of alcoholic potassium hydroxide.

The blowing agent most widely employed at present for the manufacture ofpolystyrene and poly(vinyl chloride) foams is CFC 12. This compound ispreferably replaced here by a vinylfluoroalkane whose perfluoroalkylradical C_(n) F_(2n+1) contains from 1 to 3 carbon atoms, for examplevinylperfluoroisopropane.

The main blowing agents currently employed for the production ofpolyolefin foams (polyethylene, polypropylene) are CFCs 11 and 12,employed by themselves or mixed with1,2-dichloro-1,1,2,2-tetrafluoroethane (CFC 114) or with hydrocarbons.CFC 11 is preferably replaced here by a vinylfluoroalkane in which theradical C_(n) F_(2n+1) contains from 3 to 6 carbon atoms, for examplevinyl-perfluoro-n-butane, and CFC 12 is preferably replaced by avinylfluoroalkane in which this radical C_(n) F_(2n+1) contains from 1to 3 carbon atoms, for example vinyl-fluoroisopropane. In thisapplication the vinylfluoroalkanes according to the invention can beemployed by themselves, mixed with each other or mixed with alkanes (forexample butane); the proportion by weight of the secondary blowing agentin such a mixture may range up to 90%.

The main blowing agents currently employed for the production ofphenolic foams are CFCs 11 and 113, employed by themselves or mixed.CFCs 11 and 113 are preferably replaced here by vinylfluoroalkane inwhich the radical C_(n) F_(2n+1) contains from 3 to 6 carbon atoms, forexample vinylperfluoro-n-hexane. In this application thevinylperfluoroalkanes according to the invention can be employed bythemselves, mixed with each other or mixed with alkanes, which may behalogenated, for example pentane, butane, perfluoropentane or1,1-dichloro-1-fluoroethane; the proportion of alkane, which may behalogenated in such a mixture may range up to 90% by weight.

The processes for the production of polystyrene or PVC foams, polyolefinfoams and phenolic foams are well known and do not need to be describedhere, since it suffices to replace the usual blowing agent (CFC 11, 12or 113) with a compound of formula (I) or a mixture of such compounds.The molar quantity of compound(s) of formula (I) to be used issubstantially the same as that of the blowing agent which they (it)replace(s).

The production of foams containing urethane groups (abbreviated to PUfoams below) with a very wide variety of mechanical properties byreacting relatively high-molecular-weight polyhydroxyl compounds and, ifdesired, low-molecular-weight chain extenders or cross-linking agentswith organic polyisocyanates in the presence of catalysts, blowingagents and, if desired, assistants and/or additives is known and isdescribed in numerous patents and other publications. An appropriatechoice of the starting components allows soft and elastic, semirigid orrigid PU foams to be produced by this process.

Neither is the production of foams containing bonded urethane andisocyanurate groups new. In this process, organic polyisocyanates arepartially cyclized and polymerized in the presence of catalysts, and theresultant polyisocyanates containing isocyanurate groups (PIR) are thenreacted with polyhydroxyl compounds in the presence of PU catalysts andblowing agents. In another procedure, the organic polyisocyanates aresimultaneously partially cyclized in the presence of substoichiometricamounts of polyhydroxyl compounds, catalysts with various actions andblowing agents, and the polyhydroxyl compounds are added onto theresultant unmodified polyisocyanates containing isocyanurate groups.

A review on the production of rigid PU foams and PU-PIR foams ispublished, for example, in the monograph by J. H. Saunders and K. C.Frisch, High Polymers, Volume XVI, Polyurethanes, Parts 1 and 2,Interscience Publishers, 1962 and 1964 respectively, and theKunststoff-Handbuch, Volume VII, Polyurethane, Carl-Hanser-Verlag,Munich, 1st edition, 1966, and 2nd edition, 1983.

Also known is the use of rigid PU or PU-PIR foams of this type for theproduction of composite or sandwich elements, which are usually built upfrom a rigid foam and at least one, preferably two, outer layerscomprising a rigid or elastic material, e.g. paper, plastic films, metalsheeting, glass nonwoven, chipboard, inter alia, and the foam-filling ofcavities in domestic appliances, such as cooling equipment, for examplerefrigerators or chest freezers, or hot-water storage tanks, with rigidfoams of this type as thermal insulators.

Blowing agents used worldwide on a large scale for the production ofheat- and cold-insulating rigid PU or PU-PIR foams arechlorofluoroalkanes, preferably trichlorofluoromethane. The onlydisadvantage of these blowing gases is environmental pollution, sincethey are suspected of participating in the depletion of the ozone layerin the stratosphere.

In order to reduce the amount of chlorofluoroalkanes, the blowing gasused is predominantly water, which reacts with the polyisocyanate toform carbon dioxide, which acts as the actual blowing agent. Rigid PUfoam formulations of this type have the disadvantage of a highconsumption of polyisocyanate merely for the reaction of the water toform the carbon dioxide. A further disadvantage is an impairment in theheat-insulation properties due to the relatively high thermalconductivity of the carbon dioxide compared with chlorofluoroalkanes.

According to EP-A-351 614, the blowing agents used may furthermore befluorinated hydrocarbons, perfluorinated hydrocarbons, sulfurhexafluoride or mixtures of at least two of these compounds. Since thesefluorinated or perfluorinated blowing agents are only sparingly solubleor insoluble in the starting components for the production of thepolyisocyanate polyaddition products, they are emulsified in at leastone organic and/or modified organic polyisocyanate, in at least onerelatively high-molecular-weight compound containing at least tworeactive hydrogen atoms or in a mixture of at least one relativelyhigh-molecular-weight compound containing at least two reactive hydrogenatoms and a low-molecular-weight chain extender and/or crosslinkingagent. This method allows cellular plastics having a uniform and finecell structure to be produced, but has the disadvantage of the narrowchoice of suitable fluorinated or perfluorinated compounds having aboiling point in the required boiling point range, and the high price ofthese blowing agents. In order to obtain cellular plastics having thetechnically desired cell structure, the choice is restricted to mixturesof perfluoropentane and perfluorohexane. A further disadvantage is thatblowing agents of this type are relatively resistant chemically, aredegraded only slowly in the atmosphere and can therefore contribute toglobal warming.

Low-boiling hydrocarbons which can be used as blowing agents are solublein the starting components for the production of the polyisocyanatepolyaddition products and give foams having a very coarse, frequentlynonuniform cell structure and increased thermal conductivity.

The mechanism of foam formation in the production of polyisocyanatepolyaddition products and the effect of surface-active assistants basedon siloxane-oxyalkylene copolymers on this reaction has been describedby B. Kanner et al. (J. of Cellular Plastics, Jan. 1969, pages 32 to39).

It is an object of the present invention to replace all or at least someof the chlorofluorocarbons known as blowing agents for the production ofrigid PU or PU-PIR foams by other, environmentally friendly blowingagents without adversely affecting the fine-celled foam structure, ascan be achieved using emulsions based on fluorinated hydrocarbons.

We have found that, surprisingly, this object is achieved by usingfluorinated olefins as the blowing agent.

The present invention accordingly provides a process for the productionof plastic foams, which comprises using at least one vinylfluoroalkaneof the formula

    CH.sub.2 ═CH--C.sub.n F.sub.2n+1

in which --C_(n) F_(2n+1) is linear or branched perfluoroalkyl and n isan integer from 1 to 6, as blowing agent and/or insulating gas, with theproviso that, if the vinylfluoroalkane is vinylperfluoro-n-butane, it isnot employed in admixture with dichloroethylene or in admixture withmore than 90% of 1,1-dichloro-1-fluoroethane.

The present invention preferably provides a process for the productionof rigid foams containing urethane groups or urethane and isocyanurategroups, by reacting

a) an organic and/or modified organic polyisocyanate with

b) at least one relatively high-molecular-weight compound containing atleast two reactive hydrogen atoms, and, if desired,

c) a low-molecular-weight chain extender and/or cross

linking agent,

in the presence of

d) a blowing agent,

e) a catalyst and, if desired,

f) assistants and/or additives,

wherein the blowing agent (d) used is at least one vinylfluoroalkane ofthe formula

    CH.sub.2 ═CH--C.sub.n F.sub.2n+1

in which n is an integer from 1 to 6, with the proviso that, if thevinylfluoroalkane is vinylperfluoro-n-butane, it is not employed inadmixture with dichloroethylene or in admixture with more than 90% of1,1-dichloro-1-fluoroethane.

The present invention furthermore provides blowing agent-containingemulsions which contain at least one vinylfluoroalkane of the formula

    CH.sub.2 ═CH--C.sub.n F.sub.2n+1

in which n is an integer from 1 to 6, (di), and at least one organicand/or modified organic polyisocyanate (a) or at least one relativelyhigh-molecular-weight compound containing at least two reactive hydrogenatoms (b), or at least one low-molecular-weight chain extender and/orcrosslinking agent (c), or a mixture of (b) and (c).

Since the vinylfluoroalkanes (di) which can be used according to theinvention are only sparingly soluble or essentially insoluble, in thenecessary amounts, in the starting components (a), (b) and, if used, (c)or in mixtures of at least two of these starting components, they areexpediently emulsified in at least one of the starting components, forexample in (a), (b) or (c), or in a mixture of (b) and (c) or (a) and ina mixture of (b) and (c), and used in the form of emulsions for theproduction of the rigid foams.

In contrast to highly fluorinated or perfluorinated, low-boilingalkanes, the vinylfluoroalkanes of the formula CH₂ ═CH--C_(n) F_(2n+1)which can be used according to the invention react very readily withhydroxyl free radicals and are therefore degraded in the loweratmosphere. It is furthermore advantageous that thevinylfluoroalkane-containing emulsions and the reaction mixtures formedtherefrom flow very readily. The molds, in particular those havingspatial shapes which are difficult to fill, can be filled more rapidlyand more uniformly, so that moldings of homogeneous cell structure andlow densities can be produced without difficulties. The rigid PU orPU-PIR foams produced by the process according to the invention in openor closed molds are fine-celled and have low thermal conductivity.

The rigid PU or PU-PIR foams are prepared by the process according tothe invention using, with the exception of blowing agent (d), thestarting components which are known per se, to which the followingdetails apply.

Suitable organic polyisocyanates (a) are conventional aliphatic,cycloaliphatic, araliphatic and preferably aromatic polyisocyanates.

The following may be mentioned as examples: alkylene diisocyanateshaving from 4 to 12 carbon atoms in the alkylene moiety, such as1,12-dodecane diisocyanate, 2-ethyltetramethylene 1,4-diisocyanate,2-methylpentamethylene 1,5-diisocyanate, tetramethylene 1,4-diisocyanateand preferably hexamethylene 1,6-diisocyanate; cycloaliphaticdiisocyanates, such as cyclohexane 1,3- and 1,4-diisocyanate and anydesired mixtures of these isomers,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophoronediisocyanate), 2,4-and 2,6-hexahydrotolylene diisocyanate and thecorresponding isomer mixtures, 4,4'-, 2,2'- and 2,4'-dicyclohexylmethanediisocyanate and the corresponding isomer mixtures, and preferablyaromatic diisocyanates and polyisocyanates, e.g. 2,4- and 2,6-tolylenediisocyanate and the corresponding isomer mixtures, 4,4'-, 2,4'- and2,2'-diphenylmethane diisocyanate and the corresponding isomer mixtures,mixtures of 4,4'- and 2,4'-diphenylmethane diisocyanates,polyphenyl-polymethylene polyisocyanates, mixtures of 4,4'-, 2,4'- and2,2'-diphenylmethane diisocyanates and polyphenyl-polymethylenepolyisocyanates (crude MDI), and mixtures of crude MDI and tolylenediisocyanates. The organic diisocyanates and polyisocyanates may beemployed individually or in the form of mixtures.

Frequently, modified polyisocyanates are also used, i.e. products whichare obtained by partial chemical reaction of organic diisocyanatesand/or polyisocyanates. Specific examples are ester-, urea-, biuret-,allophanate-, carbodiimide-, isocyanurate- and/or urethane-containingdiisocyanates and/or polyisocyanates. Individual examples areurethane-containing organic, preferably aromatic, polyisocyanatescontaining from 33.6 to 15% by weight, preferably from 31 to 21% byweight, of NCO, based on the total weight, for example4,4'-diphenylmethane diisocyanate, or 2,4- or 2,6-tolylene diisocyanatemodified by means of low-molecular-weight diols, triols, dialkyleneglycols, trialkylene glycols or polyoxyalkylene glycols having molecularweights of up to 1500, specific examples of di- and polyoxyalkyleneglycols, which can be employed individually or as mixtures, beingdiethylene glycol, dipropylene glycol, polyoxyethylene glycol or triol,polyoxypropylene glycol or triol and polyoxypropylene-polyoxyethyleneglycol or triol. NCO-containing prepolymers containing from 25 to 9% byweight, preferably from 21 to 14% by weight, of NCO, based on the totalweight, and prepared from the polyester- and/or preferablypolyether-polyols described below and 4,4'-diphenylmethane diisocyanate,mixtures of 2,4'- and 4,4'-diphenylmethane diisocyanate, 2,4- and/or2,6-tolylene diisocyanates or crude MDI are also suitable. Furthermore,liquid polyisocyanates containing carbodiimide groups and/orisocyanu-rate rings and containing from 33.6 to 15% by weight,preferably from 31 to 21% by weight, of NCO, based on the total weight,e.g. based on 4,4'-, 2,4' - and/or 2,2'-diphenylmethane diisocyanateand/or 2,4- and/or 2,6-tolylene diisocyanate, have also provensuccessful.

The modified polyisocyanates, if desired, may be mixed with one anotheror with unmodified organic polyisocyanates, e.g. 2,4'- or4,4'-diphenylmethane diisocyanate, crude MDI or 2,4- and/or 2,6-tolylenediisocyanate.

Organic polyisocyanates which have proven particularly successful andare therefore preferred for use for the production of rigid PU foams aremixtures of tolylene diisocyanates and crude MDI or mixtures of modifiedurethane-containing organic polyisocyanates containing from 33.6 to 15%by weight of NCO, in particular based on tolylene diisocyanates,4,4'-diphenylmethane diisocyanate, diphenylmethane diisocyanate isomermixtures or crude MDI, in particular crude MDI having a diphenylmethanediisocyanate isomer content of from 30 to 80% by weight, preferably from30 to 55% by weight.

The relatively high-molecular-weight compound (b) containing at leasttwo reactive hydrogen atoms is preferably a polyhydroxyl compound havinga functionality of from 2 to 8, preferably from 3 to 8, and a hydroxylnumber of from 150 to 850, preferably from 200 to 600.

Examples which may be mentioned are polythioether-polyols,polyester-amides, hydroxyl-containing polyacetals andhydroxyl-containing aliphatic polycarbonates and preferablypolyester-polyols and polyetherpolyols. Also used are mixtures of atleast two of the said polyhydroxyl compounds, so long as they have amean hydroxyl number within the abovementioned range.

Suitable polyester-polyols may be prepared, for example, from organicdicarboxylic acids having from 2 to 12 carbon atoms, preferablyaliphatic dicarboxylic acids having from 4 to 6 carbon atoms, andpolyhydric alcohols, preferably diols, having from 2 to 12 carbon atoms,preferably from 2 to 6 carbon atoms. Examples of suitable dicarboxylicacids are succinic acid, glutaric acid, adipic acid, suberic acid,azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid,fumaric acid, phthalic acid, isophthalic acid and terephthalic acid. Thedicarboxylic acids may be used either individually or mixed with oneanother. The free dicarboxylic acids may also be replaced by thecorresponding dicarboxylic acid derivatives, for example dicarboxylicacid mono- or diesters of alcohols having from 1 to 4 carbon atoms ordicarboxylic anhydrides. Preference is given to dicarboxylic acidmixtures comprising succinic acid, glutaric acid and adipic acid inratios of, for example, from 20 to 35 : 35 to 50 : 20 to 32 parts byweight, and in particular adipic acid. Examples of dihydric andpolyhydric alcohols, in particular diols, are ethanediol, diethyleneglycol, 1,2- and 1,3-propanediol, dipropylene glycol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, 1,10decanediol, glycerol andtrimethylolpropane. Preference is given to ethanediol, diethyleneglycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and mixtures ofat least two of said diols, in particular mixtures of 1,4-butanediol,1,5-pentanediol and 1,6-hexanediol. Furthermore, polyester-polyols madefrom lactones, e.g. ε-caprolactone, or hydroxycarboxylic acids, e.g.ω-hydroxycaproic acid, may also be employed.

The polyester-polyols may be prepared by polycondensing the organic,e.g. aromatic and preferably aliphatic polycarboxylic acids and/orderivatives thereof and polyhydric alcohols without using a catalyst orpreferably in the presence of an esterification catalyst, expediently inan inert gas atmosphere, e.g. nitrogen, carbon dioxide, helium, argon,inter alia, in the melt at from 150° to 250° C., preferably from 180° to220° C., at atmospheric pressure or under reduced pressure until thedesired acid number, which is advantageously less than 10, preferablyless than 2, is reached. In a preferred embodiment, the esterificationmixture is polycondensed at the abovementioned temperatures underatmospheric pressure and subsequently under a pressure of less than 500mbar, preferably from 50 to 150 mbar, until an acid number of from 80 to30, preferably from 40 to 30, has been reached. Examples of suitableesterification catalysts are iron, cadmium, cobalt, lead, zinc,antimony, magnesium, titanium and tin catalysts in the form of metals,metal oxides or metal salts. However, the polycondensation may also becarried out in the liquid phase in the presence of diluents and/orentrainers, e.g. benzene, toluene, xylene or chlorobenzene, for removalof the water of condensation by azeotropic distillation.

The polyester-polyols are advantageously prepared by polycondensing theorganic polycarboxylic acids and/or derivatives thereof with polyhydricalcohols in a molar ratio of from 1:1 to 1.8, preferably from 1:1.05 to1.2.

The polyester-polyols obtained preferably have a functionality of from 2to 3, and a hydroxyl number of from 150 to 400, in particular from 200to 300.

However, the preferred polyhydroxyl compounds are polyether-polyolsprepared by conventional processes, for example by anionicpolymerization using alkali metal hydroxides, such as sodium hydroxideor potassium hydroxide, or alkali metal alkoxides, such as sodiummethoxide, sodium ethoxide, potassium ethoxide or potassium isopropoxideas catalysts and using at least one initiator molecule containing from 2to 8, preferably from 3 to 8, bonded reactive hydrogen atoms, or bycationic polymerization using Lewis acids, such as antimonypentachloride, boron fluoride etherate, inter alia, or bleaching earthas catalysts, from one or more alkylene oxides having from 2 to 4 carbonatoms in the alkylene moiety.

Examples of suitable alkylene oxides are tetrahydrofuran, 1,3-propyleneoxide, 1,2- and 2,3-butylene oxide, styrene oxide and preferablyethylene oxide and 1,2-propylene oxide. The alkylene oxides may be usedindividually, alternately one after the other or as mixtures. Examplesof suitable initiator molecules are water, organic dicarboxylic acids,such as succinic acid, adipic acid, phthalic acid and terephthalic acid,aliphatic and aromatic, unsubstituted or N-mono-, N,N-andN,N'-dialkyl-substituted diamines having from 1 to 4 carbon atoms in thealkyl moiety, such as unsubstituted or mono- or dialkyl-substitutedethylenediamine, diethylenetriamine,triethylenetetramine,1,3-propylenediamine, 1,3- and 1,4-butylenediamine,1,2-, 1,3-, 1,4-, 1,5- and 1,6-hexamethylenediamine, phenylenediamines,2,3-, 2,4-and 2,6-tolylenediamine and 4,4'-, 2,4'- and2,2'-diaminodiphenylmethane.

Other suitable initiator molecules are alkanolamines, e.g. ethanolamine,diethanolamine, N-methyl- and N-ethyl-ethanolamine, N-methyl- andN-ethyl-diethanolamine, and triethanolamine, and ammonia. Preference isgiven to polyhydric alcohols, e.g. dihydric or in particular trihydricand/or polyhydric alcohols, such as ethanediol, 1,2- and1,3-propanediol, diethylene glycol, dipropylene glycol, 1,4-butanediol,1,6-hexanediol, glycerol, trimethylolpropane, pentaerythritol, sorbitoland sucrose.

The polyether-polyols preferably have a functionality of from 3 to 8, inparticular from 3 to 6, and hydroxyl numbers of from 200 to 850, inparticular from 300 to 600.

Other suitable polyether-polyols are the melamine/polyether-polyoldispersions of EP-A-23 987 (U.S. Pat. No. 4,293,657), thepolymer/polyether-polyol dispersions prepared from polyepoxides andepoxy resin curing agents in the presence of polyether-polyols inaccordance with DE-A-29 43 689 (U.S. Pat. No. 4,305,861), thedispersions of aromatic polyesters in polyhydroxyl compounds of EP-A-62204 (U.S. Pat. No. 4,435,537) or DE-A-33 00 474, the dispersions oforganic and/or inorganic fillers in polyhydroxyl compounds of EP-A-11751 (U.S. Pat. No. 4,243,755), the polyurea/polyether-polyol dispersionsof DE-A-31 25 402, the tris(hydroxyalkyl) isocyanurate/polyether-polyoldispersions of EP-A-136 571 (U.S. Pat. No. 4,514,526) and thecrystallite suspensions of DE-A-33 42 176 and DE-A-33 42 177 (U.S. Pat.No. 4,560,708); the information given in said patents should be regardedas part of the description of the present application.

Like the polyester-polyols, the polyether-polyols can be usedindividually or in the form of mixtures. Furthermore, they may be mixedwith the abovementioned dispersions, suspensions or polyester-polyolsand the hydroxyl-containing polyester-amides, polyacetals and/orpolycarbonates.

Examples of suitable hydroxyl-containing polyacetals are the compoundswhich can be prepared from glycols, such as diethylene glycol,triethylene glycol, 4,4'-dihydroxyethoxydiphenyldimethylmethane,hexanediol and formaldehyde. Suitable polyacetals can also be preparedby polymerizing cyclic acetals.

Suitable hydroxyl-containing polycarbonates are those of a conventionaltype, which can be prepared, for example, by reacting diols, such as1,3-propanediol, 1,4-butanediol and/or 1,6-hexanediol, diethyleneglycol, triethylene glycol or tetraethylene glycol, with diarylcarbonates, e.g. diphenyl carbonate, or phosgene.

The polyester-amides include, for example, the predominantly linearcondensates obtained from polybasic, saturated and/or unsaturatedcarboxylic acids or anhydrides thereof and amino alcohols, or mixturesof polyhydric alcohols and amino alcohols and/or polyamines.

Polyhydroxyl compounds which have proven particularly successful and aretherefore preferred are mixtures expediently containing, based on 100parts by weight,

bi) from 0 to 95 parts by weight, preferably from 20 to 80 parts byweight, of a sucrose-initiated polyether-polyol having a hydroxyl numberof from 300 to 500, preferably from 350 to 450, based on 1,2-propyleneoxide or 1,2-propylene oxide and ethylene oxide,

bii) from 0 to 15 parts by weight, preferably from 5 to 15 parts byweight, of a sorbitol-initiated polyether-polyol having a hydroxylnumber of from 400 to 600, preferably from 450 to 550, based on1,2-propylene oxide or 1,2-propylene oxide and ethylene oxide,

biii) from 0 to 20 parts by weight, preferably from 5 to 15 parts byweight, of an ethylenediamine-initiated polyether-polyol having ahydroxyl number of from 700 to 850, preferably from 750 to 800, based on1,2-propylene oxide, and

biiii) from 0 to 60 parts by weight, preferably from 5 to 40 parts byweight, of a polyether-polyol having a hydroxyl number of from 400 to600, preferably from 450 to 550, based on 1,2-propylene oxide or1,2-propylene oxide and ethylene oxide and prepared using a mixture ofsucrose and triethanolamine in a weight ratio of from 1:2 to 2:1 asinitiator molecules.

The rigid PU or PU-PIR foams may be prepared with or without the use ofchain extenders and/or crosslinking agents (c). However, it may proveadvantageous, in order to modify the mechanical properties, to add chainextenders, crosslinking agents or, if desired, mixtures thereof. Thechain extenders and/or crosslinking agents used are preferablyalkanolamines, in particular diols and/or triols, having a molecularweight of less than 400, preferably from 60 to 300. Examples arealkanolamines, e.g. trialkanolamines such as triethanolamine,triisopropanolamine and products of the addition reaction of ethyleneoxide or 1,2-propylene oxide and alkylenediamines having from 2 to 6carbon atoms in the alkylene moiety, e.g.N,N,N',N'-tetra(2-hydroxyethyl)-ethylenediamine andN,N,N',N'-tetra(2-hydroxypropyl)-ethylenediamine, aliphatic,cycloaliphatic and/or araliphatic diols having from 2 to 14 carbonatoms, preferably from 4 to 10 carbon atoms, e.g. ethylene glycol,1,3-propanediol, 1,10-decanediol, o-, m- and p-dihydroxycyclohexane,diethylene glycol, dipropylene glycol and preferably 1,4-butanediol,1,6-hexanediol and bis(2-hydroxyethyl)hydroquinone, triols, such as1,2,4- and 1,3,5-trihydroxycyclohexane, glycerol and trimethylolpropane,and low-molecular-weight hydroxyl-containing polyalkylene oxides, basedon ethylene oxide and/or 1,2-propylene oxide and aromatic diamines, e.g.tolylenediamines and/or diaminodiphenylmethanes, and the abovementionedalkanolamines, diols and/or triols as initiator molecules.

The amount of chain extender, crosslinking agent or mixture thereofused, if any, for the production of the rigid PU or PU-PIR foams isexpediently from 0 to 20% by weight, preferably from 2 to 8% by weight,based on the weight of the polyhydroxyl compound.

The blowing agent (d) used for the production of the rigid PU or PU-PIRfoam is according to the invention a vinylfluoroalkane of the formula

    CH.sub.2 ═CH--C.sub.n F.sub.2n+1

in which n is an integer from 1 to 6, preferably from 3 to 5, inparticular 3 or 4. Specific examples of suitable vinylfluoroalkanes arevinylperfluoromethane, vinylperfluoroethane, vinylperfluoro-n- or-isopropane, vinylperfluorobutane, vinylperfluoro-sec.-butane,vinylperfluoropentane and vinylperfluorohexane. The vinylfluoralkane(di) can be used alone or in a mixture.

Also suitable are mixtures of the appropriate vinylperfluoro-n- and-isoalkanes or technical-grade mixtures thereof. Blowing agents (d)which have proven particularly successful, and ones which are thereforepreferred, are vinylperfluoroisopropane and vinylperfluorobutane.

Since the vinylfluoroalkane (di) which can be used according to theinvention is, as stated above, only sparingly soluble or essentiallyinsoluble, in the necessary amounts, in starting components (a), (b) and(c) or in a mixture of at least two of these starting components, it ispreferably emulsified in one of the starting components (a), (b) and, ifused, (c) or in a mixture of at least two of these. Thevinylfluoroalkane or the mixture of vinylfluoroalkanes is usually usedin an amount of from 1 to 40 parts by weight, preferably from 1 to 15parts by weight, in particular from 2 to 10 parts by weight, based on100 parts by weight of the starting components (a) and (b) or (a) to(c).

The vinylfluoroalkane (di) may be employed as the only blowing agent.However, the vinylfluoroalkane (di) or vinylfluoroalkane emulsion whichcan be used according to the invention can also be used in combinationwith other, physical, inert blowing agents or chemical blowing agents(dii) which are different from (di), or in combination with a mixture ofphysical and chemical blowing agents which are different from (di).

A suitable blowing agent mixture (d) for the production of the rigidfoams containing urethane groups or urethane and isocyanurate groups bythe process according to the invention can thus preferably contain orcomprise

di) at least one vinylfluoroalkane of the formula

    CH.sub.2 ═CH--C.sub.n F.sub.2n+1

in which n is an integer from 1 to 6, in particular 3 or 4, or a mixturethereof, and

dii) at least one further physical blowing agent which is different from(di) or a chemical blowing agent, or a mixture of such physical andchemical blowing agents.

Examples of suitable physical blowing agents are:

alkanes having 4 to 12 carbon atoms, preferably 5 to 8 carbon atoms,

cycloalkanes having 4 to 6 carbon atoms, preferably 5 or 6 carbon atoms,

linear or cyclic, saturated or olefinically unsaturated ethers having 2to 5 carbon atoms,

aliphatic carboxylic acid esters having a maximum boiling point of 142°C., preferably below 80° C., aliphatic and/or cycloaliphatic ketoneshaving 3 to 5 carbon atoms,

partially halogenated chlorofluorocarbons having 1 or 2 carbon atoms,

partially fluorinated or preferably perfluorinated tertiary alkylamineshaving 3 to 9 carbon atoms, preferably 4 to 6 carbon atoms,

partially fluorinated or perfluorinated, linear or cyclic ethers having2 to 12 carbon atoms, preferably 3 to 6 carbon atoms, and

preferably fluorinated or perfluorinated, advantageously aliphatic orcycloaliphatic hydrocarbons having 3 to 8 carbon atoms, preference beinggiven to aliphatic or cycloaliphatic, fluorinated hydrocarbons having 4to 6 carbon atoms which are liquid at room temperature and contain atleast one bonded hydrogen atom, and aliphatic or cycloaliphatic,perfluorinated hydrocarbons having 4 to 7 carbon atoms.

Specific examples of physical blowing agents (dii) of the said type aregaseous or preferably liquid, linear or branched alkanes, e.g. butane,n- and isopentane and technical-grade pentane mixtures, n- andisohexanes, n- and isoheptanes, n- and isooctanes, n- and isononanes, n-and isodecanes, n- and isoundecanes and n- and isododecanes. Since verygood results with respect to the stability of the emulsions, theprocessing properties of the reaction mixture and the mechanicalproperties of the rigid foams containing urethane groups or urethane andisocyanurate groups are achieved when n-pentane, isopentane, n-hexane,or isohexane or a mixture thereof, is used, these alkanes are preferablyemployed. Furthermore, specific examples of cycloalkanes arecyclobutane, preferably cyclopentane, cyclohexane or mixtures thereof,specific examples of linear or cyclic ethers are dimethyl ether, diethylether, methyl ethyl ether, vinyl methyl ether, vinyl ethyl ether,divinyl ether, tetrahydrofuran and furan, specific examples of aliphaticcarboxylic acid esters are methyl, ethyl, n-propyl, isopropyl and butylacetate and preferably methyl and ethyl formate, specific examples ofketones are acetone, methyl ethyl ketone and cyclopentanone, specificexamples of partially halogenated chlorofluorocarbons aredifluoromonochloromethane (R 22), 1,1,1-trifluoro-2,2-dichloroethane (R123) and 1,1,1-dichloromonofluoroethane (R 141b), specific examples offluorinated or perfluorinated, tertiary alkylamines areperfluorodimethylethylamine, perfluorodiethylmethylamine,perfluorotrimethylamine, perfluorotriethylamine,perfluorodimethyl-n-propylamine, perfluorodiethyl-n-propylamine andpreferably perfluorodimethylisopropylamine and the correspondingpartially fluorinated tertiary alkylamines, specific examples ofpartially fluorinated or perfluorinated, linear or cyclic ethers are2,2,2-trifluoroethyl methyl ether (CF₃ CH₂ OCH₃), 2,2,2-trifluoroethyldifluoromethyl ether (CF₃ CH₂ OCHF₂), perfluorodiethyl ether,perfluorodipropyl ether and perfluoroethyl propyl ether, oligomers ofperfluoropropylene oxide having a maximum boiling point of 140° C.,perfluorotetrahydrofuran, perfluoroalkyltetrahydrofurans andperfluorofuran. Aliphatic or cycloaliphatic, fluorinated orperfluorinated hydrocarbons which are gases at room temperature, e.g.perfluoropropane, perfluorobutane or perfluorocyclobutane, which can beliquefied under pressure, for example up to about 25 bar, mixed andemulsified are also highly suitable.

However, physical blowing agents (dii) which have proven eminentlysuitable and are therefore preferred are aliphatic or cycloaliphatic,fluorinated or perfluorinated hydrocarbons which are liquid at roomtemperature. The fluorinated hydrocarbons used are expediently thosewhich are predominantly, for example at least 85%, fluorinated andcontain at least one, preferably one, bonded hydrogen atom. Examples ofsuitable fluorinated hydrocarbons are trifluoromethane, difluoromethane,difluoroethane, tetrafluoroethane and preferably hexafluoropropane,heptafluoropropane, 1-H-perfluorobutane and 1-H-perfluorohexane.Examples of suitable perfluorinated hydrocarbons are perfluoropentane,perfluorohexane, perfluoroheptane, perfluorooctane,perfluorocyclopentane and perfluorocyclohexane. The fluorinated orperfluorinated hydrocarbons or mixtures thereof, like the other suitablephysical blowing agents, can be employed individually or in the form ofmixtures. It is also possible to use mixtures of the different physicalblowing agents.

Examples of blowing agent mixtures of this type which may be mentionedare those which contain

di) at least one vinylfluoroalkane from the group comprisingvinylperfluoroisopropane and preferably vinylperfluoro-n-butane, and

dii) at least one partially fluorinated hydrocarbon from the groupcomprising hexafluoropropane, heptafluoropropane, 1-H-perfluorobutaneand 1-H-perfluorohexane, and/or at least one partially fluorinated etherfrom the group comprising 2,2,2-trifluoroethyl methyl ether and2,2,2-trifluoroethyl difluoromethyl ether.

The blowing agent mixtures (d) which can be used according to theinvention advantageously contain the vinylfluoroalkane (di) and thefurther physical blowing agent (dii), preferably the fluorinated and/orperfluorinated hydrocarbon, in a weight ratio of from 90:10 to 10:90,preferably from 80:20 to 60:40. If the other physical blowing agent(dii) is insoluble in the starting components (a), (b) and (c) in thenecessary amounts, it is expediently emulsified in at least one of thesestarting components together with the vinylfluoroalkanes (di).

In addition to the vinylfluoroalkanes (di) which can be used accordingto the invention as blowing agent, or a mixture of (di) and anotherphysical blowing agent (dii) which is different from (di), or in placeof the physical blowing agent which is different from (di), it is alsopossible to use a chemical blowing agent. A particularly proven chemicalblowing agent is water, which reacts with the organic, modified orunmodified polyisocyanate (a) to form carbon dioxide, the actual blowingagent and urea groups, and thus effects the compressive strength of theend products. Other suitable chemical blowing agents are organic mono-and polycarboxylic acids having a molecular weight of from 60 to 300 andpreferably formic acid, and ammonium and/or amine salts of formic acidand/or of the abovementioned mono- and/or polycarboxylic acids, so longas these react with isocyanates under the reaction conditions and formcarbon dioxide.

The organic carboxylic acids used are advantageously aliphatic mono- andpolycarboxylic acids, e.g. dicarboxylic acids. However, other organicmono- and polycarboxylic acids are also suitable. The organic carboxylicacids may, if desired, also contain bonded substituents which are inertunder the reaction conditions of the polyisocyanate polyaddition or arereactive with isocyanate, and/or may contain olefinically unsaturatedgroups. Specific examples of chemically inert substituents are halogenatoms, such as fluorine and/or chlorine, and alkyl, e.g. methyl orethyl. The substituted organic carboxylic acids expediently contain atleast one further group which is reactive toward isocyanates, e.g. amercapto group, a primary and/or secondary amino group or preferably aprimary and/or secondary hydroxyl group.

Suitable carboxylic acids are thus substituted or unsubstitutedmonocarboxylic acids, e.g. acetic acid, propionic acid,2-chloropropionic acid, 3-chloropropionic acid, 2,2-dichloropropionicacid, hexanoic acid, 2-ethylhexanoic acid, cyclohexanecarboxylic acid,dodecanoic acid, palmitic acid, stearic acid, oleic acid,3-mercaptopropionic acid, glycolic acid, 3-hydroxypropionic acid, lacticacid, ricinoleic acid, 2-aminopropionic acid, benzoic acid,4-methylbenzoic acid, salicylic acid and anthranilic acid, andsubstituted or unsubstituted polycarboxylic acids, preferablydicarboxylic acids, e.g. oxalic acid, malonic acid, succinic acid,fumaric acid, maleic acid, glutaric acid, adipic acid, sebacic acid,dodecanedioic acid, tartaric acid, phthalic acid, isophthalic acid andcitric acid.

The amine salts are usually formed using weakly basic amines, e.g.triethylamine, dimethylbenzylamine or hydrazine.

Since the amount of water present as a byproduct in the polyester- andpolyether-polyols is frequently sufficient, there is frequently no needto add any further chemical blowing agent. However, water is preferablyadditionally introduced into the polyurethane formulation, usually in anamount of from 0.05 to 5% by weight, preferably from 0.5 to 4% byweight, based on the weight of starting components (a) to (c).

Suitable blowing agent mixtures (d) thus expediently contain, based onthe total weight of (di) and (dii),

di) at least 30% by weight, preferably at least 50% by weight, of atleast one vinylfluoroalkane (di), and

dii) a maximum of 70% by weight, preferably less than 50% by weight, ofat least one further physical and/or chemical blowing agent (dii) whichis different from (di).

Examples of blowing agent mixtures which may be mentioned contain

di) at least one vinylfluoroalkane from the group comprisingvinylperfluoroisopropane and preferably vinylperfluoro-n-butane, and

dii) water and, if desired, at least one partially fluorinatedhydrocarbon from the group comprising hexafluoropropane,heptafluoropropane, 1-H-perfluorobutane and 1-H-perfluorohexane, and/orat least one partially fluorinated ether from the group comprising2,2,2-trifluoroethyl methyl ether and 2,2,2-trifluoroethyldifluoromethyl ether.

The most expedient amount of vinylfluoroalkane (di) as blowing agent forthe production of the rigid foams containing urethane groups or urethaneand isocyanurate groups depends on the desired density and on whetherany water is employed as the preferred chemical blowing agent. Thenecessary amount of blowing agent can easily be determinedexperimentally. In general, amounts of from 1 to 40 parts by weight,preferably from 1 to 15 parts by weight, in particular from 3 to 10parts by weight, of the vinylfluoroalkane (di) or preferably of theblowing agent mixture comprising (di) and (dii), based on 100 parts byweight of the starting components (a) to (c) or (a) and (b), givesatisfactory results.

The vinylfluoroalkane (di) of the formula CH₂ ═CH--C_(n) F_(2n+1) whichcan be used according to the invention as the blowing agent (d), or theblowing agent mixture of a vinylfluoroalkane (di) and a further,physical and/or chemical blowing agent (dii) which is different from(di), is, for processing, preferably emulsified in the startingcomponents (a), (b) and (c) or a mixture of (b) and (c) or in (a) and(b), the soluble physical or chemical blowing agent (dii) of the blowingagent mixture (d) dissolving homogeneously in the starting components.

The emulsifiers known from polyurethane chemistry are suitable forproducing blowing agent-containing emulsions of this type. Theemulsifiers employed are in particular oligomeric acrylates containingbonded polyoxyalkylene and fluoroalkane radicals as side groups andhaving a fluorine content of from approximately 5 to 30% by weight.Oligomeric acrylates of this type are sufficiently well known frompolymer chemistry, for example as adhesion promoters in reinforcedplastics, and further details are thus superfluous. Their structure andprocesses for their preparation, and suitable fluoroaliphatic radicalsand precursors containing active hydrogen which can be used for thepreparation of the oligomers described are described in detail, forexample, in DE-B-23 10 357 and U.S. Pat. No. 3,787,351, which isequivalent thereto, and in the patents and literature cited therein, andin DE-A-38 24 355. The statements made in these publications, inparticular in U.S. Pat. No. 3,787,351, are incorporated fully into theapplication description and are regarded as a constituent thereof.

The oligomeric acrylates containing polyoxyalkylene and fluoroalkaneradicals as side groups which are suitable, for example, as emulsifiersare expediently employed in an amount of from 0.01 to 6 parts by weight,preferably from 0.2 to 3.5 parts by weight, in particular from 0.5 to2.0 parts by weight, based on 100 parts by weight of the startingcomponents (a), (b) and (c) or the mixture of (b) and (c).

Suitable compounds for the emulsification of the vinylfluoroalkane (di)or the blowing agent mixture comprising (di) and (dii) are, as statedabove, the organic and/or modified organic polyisocyanate (a), therelatively high-molecular-weight compound containing at least tworeactive hydrogen atoms (b) and the low-molecular-weight chain extenderand/or crosslinking agent (c). Mixtures of (b) and low-molecular-weightchain extenders and/or crosslinking agents (c) are also suitable.

If an organic and/or modified organic polyisocyanate (a) is used as theother emulsion phase, preference is given to aromatic polyisocyanatesselected from the group comprising 2,4- and 2,6-tolylene diisocyanatesand mixtures of said isomers, 4,4'-, 2,4'- and 2,2'-diphenylmethanediisocyanates and mixtures of at least two of said isomers, and mixturesof diphenylmethane diisocyanates and polyphenyl-polymethylenepolyisocyanates. If the organic polyisocyanates are crystalline at roomtemperature, they are liquefied by mixing with liquid polyisocyanatesand/or by suitable partial modification, e.g. carbodiimidization and/orurethanization.

However, the other emulsion phase is preferably the relativelyhigh-molecular-weight compound containing at least two reactive hydrogenatoms (b). Particularly suitable are polyester-polyols or mixturesthereof having a functionality of from 2 to 3 and a molecular weight offrom 480 to 3000 and polyether-polyols or mixtures thereof having afunctionality of from 2 to 6 and a molecular weight of from 400 to 8000,these expediently being selected from the group comprising thepolyoxyethylene-, polyoxypropylene- andpolyoxypropylene-polyoxyethylene-polyols and polyoxytetramethyleneglycols, or mixtures thereof.

The blowing agent-containing emulsion according to the invention thuspreferably contains or comprises at least one vinylfluoroalkane of theformula CH₂ ═CH--C_(n) F_(2n+1) in which n is an integer from 1 to 6,(di), and at least one organic and/or modified organic polyisocyanate(a) or at least one relatively high-molecular-weight compound containingat least two reactive hydrogen atoms (b), or at least onelow-molecular-weight chain extender and/or crosslinking agent (c), or amixture of (b) and (c).

Particularly successful blowing agent-containing emulsions are thosewhich comprise

from 1 to 40 parts by weight, preferably from 2 to 15 parts by weight,based on 100 parts by weight of (b) or (b) and (c), of one or morevinylfluoroalkanes of the formula CH₂ ═CH--C_(n) F_(2n+1) in which n isan integer from 1 to 6, (di),

from 0 to 5 parts by weight, preferably from 1.5 to 3.5 parts by weight,based on 100 parts by weight of (b) or (b) and (c), of water, (dii),

from 0 to 36 parts by -weight, preferably from 1 to 7 parts by weight,based on 100 parts by weight, of (b) or (b) and (c), of at least onefurther physical blowing agent (dii) which is different from (di) and isonly sparingly soluble or insoluble in the starting components (a), (b)and (c), preferably a fluorinated or perfluorinated organic compound(dii) which contains no bonded olefinically unsaturated groups in themolecule, and at least one relatively high-molecular-weight compoundcontaining at least two reactive hydrogen atoms (b), or a mixture of (b)and a low-molecular-weight chain extender and/or crosslinking agent (c).

Particularly preferred emulsions are those of said type in which thevinylfluoroalkane (di) is vinylperfluoroisopropane and/orvinylperfluoro-n-butane.

To prepare the blowing agent-containing emulsions, the startingcomponents (a), (b) or (c) or a mixture of (b) and (c) and thevinylfluoroalkane or vinylfluoroalkane-containing blowing agent mixture(d) is mixed vigorously, expediently in the presence of an emulsifier,preferably an oligomeric acrylate, at from 0° to 70° C., preferably from20° to 40° C. Examples of suitable mixing units for this purpose arestatic mixers, e.g. an SMX from Sulzer (Switzerland), or dynamic mixers,e.g. propeller stirrers or Ultra-Turrax® from Hanke und Kunkel(Germany).

The catalysts (e) used to produce the rigid PU or PU-PIR foams are, inparticular, compounds which greatly accelerate the reaction of thehydroxyl-containing compound of the starting components (b) and, ifused, (c) with the organic, modified or unmodified polyisocyanate (a).Examples of suitable compounds are organometallic compounds, preferablyorganotin compounds, such as tin(II) salts of organic carboxylic acids,e.g. tin(II) acetate, tin(II) octanoate, tin(II) ethylhexanoate andtin(II) laurate, and dialkyltin(IV) salts of organic carboxylic acids,e.g. dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate anddioctyltin diacetate, organic amidines, such as2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tertiary amines, such astriethylamine, tributylamine, dimethylbenzylamine, N-methyl-, N-ethyl-,N-cyclohexylmorpholine, N,N,N',N,-tetramethylethylenediamine,N,N,N',N,-tetramethylbutanediamine,N,N,N',N,-tetramethyl-1,6-hexanediamine, pentamethyldiethylenetriamine,tetramethyldiaminoethyl ether, bis(dimethylaminopropyl)urea,dimethylpiperazine, 1,2-dimethylimidazole, 1-azabicyclo[3.3.0]octaneand, preferably, 1,4-diazabicyclo[2.2.2]octane and alkanolaminecompounds such as triethanolamine, triisopropanolamine, N-methyl- andN-ethyldiethanolamine and dimethylethanolamine.

Other suitable catalysts aretris(dialkylaminoalkyl)-s-hexahydrotriazines, in particulartris(N,N-dimethylaminopropyl)-s-hexahydrotriazine, tetraalkylammoniumhydroxides, such as tetramethylammonium hydroxide, alkali metalhydroxides, such as sodium hydroxide, and alkali metal alkoxides, suchas sodium methoxide and potassium isopropoxide, and alkali metal saltsof longchain fatty acids having from 10 to 20 carbon atoms and possiblycontaining lateral OH groups. From 0.001 to 5% by weight, in particularfrom 0.05 to 2% by weight, of catalyst or catalyst combination ispreferably used, based on the weight of component (b). Theorganometallic compound and the highly basic amine, preferably tertiaryamine, can in each case be employed as the only catalyst or incombination with one another.

If desired, assistants and/or additives (f) can be incorporated into thereaction mixture for the production of the rigid PU or PU-PIR foams.Specific examples are surfactants, foam stabilizers, cell regulators,fillers, dyes, pigments, flameproofing agents, hydrolysis-protectionagents, and fungistatic and bacteriostatic substances.

Examples of suitable surfactants are compounds which serve to supporthomogenization of the starting materials and may also regulate the cellstructure. Specific examples are emulsifiers, such as the sodium saltsof castor oil sulfates, or of fatty acids and the salts of fatty acidswith amines, for example diethylamine oleate, diethanolamine stearateand diethanolamine ricinoleate, salts of sulfonic acids, e.g. alkalimetal salts or ammonium salts of dodecylbenzene- ordinaphthylmethanedisulfonic acid and ricinoleic acid; foam stabilizers,such as siloxane-oxyalkylene copolymers and other organopolysiloxanes,oxyethylated alkylphenols, oxyethylated fatty alcohols, paraffin oils,castor oil esters, ricinoleic acid esters, Turkey red oil and groundnutoil, and cell regulators, such as paraffins, fatty alcohols anddimethylpolysiloxanes. Suitable compounds for improving theemulsification action, the cell structure and/or stabilizing the foamare furthermore oligomeric polyacrylates containing polyoxyalkylene andfluoroalkane radicals as side groups. The surfactants are usually usedin amounts of from 0.01 to 5 parts by weight, based on 100 parts byweight of component (b).

For the purposes of the invention, fillers, in particular reinforcingfillers, are conventional organic and inorganic fillers, reinforcingagents, wetting agents, agents for improving the abrasion behavior inpaints, coating agents, etc. Specific examples are inorganic fillers,such as silicate minerals, for example phyllosilicates, such asantigorite, serpentine, hornblendes, amphiboles, chrysotile, and talc;metal oxides, such as kaolin, aluminum oxides, aluminum silicate,titanium oxides and iron oxides, metal salts, such as chalk, barytes andinorganic pigments, such as cadmium sulfide, zinc sulfide and glassparticles. Examples of suitable organic fillers are carbon black,melamine, colophony, cyclopentadienyl resins and graft polymers.

The inorganic and organic fillers may be used individually or asmixtures and are advantageously introduced into the reaction mixture inamounts of from 0.5 to 50% by weight, preferably from 1 to 40% byweight, based on the weight of components (a) to (c).

Examples of suitable flameproofing agents are diphenyl cresyl phosphate,tricresyl phosphate, tris(2chloroethyl) phosphate, tris(2-chloropropyl)phosphate, tris(1,3-dichloropropyl) phosphate, tris(2,3-dibromopropyl)phosphate, tetrakis(2-chloroethyl)ethylene diphosphate, dimethylmethanephosphonate, diethyl diethanolaminomethyl phosphonate and commerciallyavailable halogen-containing flameproofing polyols.

In addition to the abovementioned halogen-substituted phosphates, it isalso possible to use inorganic flameproofing agents, such as redphosphorus, aluminum oxide hydrate, antimony trioxide, arsenic oxide,ammonium polyphosphate and calcium sulfate, or expandable graphite orcyanuric acid derivatives, e.g. melamine, or mixtures of two or moreflameproofing agents, e.g. ammonium polyphosphates, expandable graphiteand melamine, and, if desired, starch, in order to flameproof the rigidPU or PU-PIR foams produced according to the invention. In general, ithas proven expedient to use from 5 to 50 parts by weight, preferablyfrom 5 to 25 parts by weight, of said flameproofing agents or mixturesper 100 parts by weight of components (a) to (c).

Further details on the other conventional assistants and additivesmentioned above can be obtained from the specialist literature, forexample from the monograph by J. H. Saunders and K. C. Frisch, HighPolymers, Volume XVI, Polyurethanes, Parts 1 and 2, IntersciencePublishers 1962 and 1964 respectively, or Kunststoff-Handbuch,Polyurethane, Volume VII, Carl-Hanser-Verlag, Munich, Vienna, 1st and2nd Editions, 1966 and 1983.

To produce the rigid PU foams, the organic, modified or unmodifiedpolyisocyanate (a), the relatively high-molecular-weight compoundcontaining at least two reactive hydrogen atoms (b) and, if used, thechain extender and/or crosslinking agent (c) are reacted in such amountsthat the ratio between the number of equivalents of NCO groups in thepolyisocyanate (a) and the total number of reactive hydrogen atoms incomponent (b) and, if used, (c) is from 0.85 to 1.25:1, preferably from0.95 to 1.15:1, in particular from 1 to 1.05:1. If the rigid foamcontaining urethane groups is modified by formation of isocyanurategroups, for example in order to increase the flame resistance, it isusual to use an NCO:OH equivalent ratio of up to 60:1, preferably from1.5 to 30:1, in particular from 1.5 to 8:1.

The rigid PU or PU-PIR foams can be produced batchwise or continuouslyby the prepolymer or preferably by the one-shot process using knownmixing equipment.

It has proven particularly advantageous to use the two-component methodand to combine the starting components (b), (d), (e) and, if used, (c)and (f) in component (A) and to use the organic or modifiedpolyisocyanate (a) or a mixture of said polyisocyanates as component(B).

The starting components are mixed at from 15° to 90° C., preferably atfrom 20° to 65° C., in particular at from 20° to 35° C., and introducedinto an open, heated or unheated mold, in which the reaction mixture isallowed to expand essentially without pressure in order to avoid acompacted peripheral zone. In order to produce PU or PU-PIR foammoldings, the partially filled mold is sealed, and the reaction mixtureis expanded, usually with compaction, for example at a degree ofcompaction of from 1.2 to 8, preferably from 1.5 to 4, and allowed tocure. In order to form composite elements, the reverse side of an outerlayer, is expediently coated, for example by pouring or spraying, withthe foamable reaction mixture, which is allowed to expand and cured toform the rigid PU or PU-PIR foam.

The rigid PU or PU-PIR foams produced by the process according to theinvention advantageously have a density of from 15 to 100 g/l,preferably from 28 to 60 g/l.

The rigid PU or PU-PIR foams are preferably used as a heat-insulatingintermediate layer in composite elements and for foam-filling cavitiesin housings for refrigeration equipment, in particular for refrigeratorsand chest freezers, and as an outer jacket for hot-water storage tanks.The products are furthermore suitable for insulating warmed materials,as an engine cover and as pipe shells.

In the examples, parts are by weight.

EXAMPLE 1 Component A

To prepare the blowing agent-containing emulsion, 9 parts by weight ofvinylperfluoro-n-butane were added with vigorous stirring using an UltraTurrax® at 23° C. to a mixture comprising

82 parts by weight of a polyoxypropylene-polyol having a hydroxyl numberof 400, prepared from sucrose as the initiator molecule and1,2-propylene oxide,

10 parts by weight of a polyoxypropylene glycol having a hydroxyl numberof 105, prepared using 1,2-propanediol as the initiator molecule,

2 parts by weight of polysiloxane foam stabilizer (Tegostab® B8406 fromGoldschmidt AG, Essen),

2 parts by weight of N,N-dimethylcyclohexylamine and 4 parts by weightof water.

A milky emulsion of the vinylperfluoro-n-butane in the polyether-polyolmixture was obtained.

Component B

A mixture of diphenylmethane diisocyanates and polyphenyl-polymethylenepolyisocyanates having an NCO content of 31% by weight (Lupranat® M20Sfrom BASF Aktiengesellschaft)

100 parts by weight of component A and

150 parts by weight of component B

were mixed with vigorous stirring at 23° C., and the foamable reactionmixture was introduced into an open, cuboid, metallic mold where it wasallowed to expand freely.

A very fine-celled rigid PU foam having a mean pore diameter of 220 μmand a density of 27 g/l was obtained. The proportion of closed cells was93% and the thermal conductivity was 19 mW/m K.

EXAMPLE 2

The procedure was similar to that of Example 1, but the foamablereaction mixture was introduced into an open, cuboid, metallic moldhaving a capacity of 8.5 l, and the mold was then closed.

256 g of the reaction mixture were required to foam-fill the moldcompletely. A molding having a minimum density of 30 g/l was obtained.

COMPARISON EXAMPLE 1

The procedure was similar to that of Example 1, but thevinylperfluoro-n-butane was replaced by 9 parts by weight ofperfluoro-n-pentane as blowing agent.

The reaction mixture was foamed as described in Example 2. 340 g of thereaction mixture were required to completely foam-fill the cuboid moldcavity of 8.5 l.

A very fine-celled rigid polyurethane foam was again obtained, but itsminimum molding density was 40 g/l.

EXAMPLE 3

The procedure was similar to that of Example 1, but the 4.0 parts byweight of water were replaced by just 0.5 part by weight of water and 10parts by weight of vinylperfluoroisopropane. The mixing ratio betweencomponents A and B was 100:109.

A very fine-celled rigid PU foam having a mean pore diameter of 180 μmand a density of 86 g/l was obtained. The proportion of closed cells was95% and the thermal conductivity was 19.5 mW/m K.

EXAMPLE 4 Component A

To prepare the blowing agent-containing emulsion, 3.8 parts by weight ofvinylperfluoro-n-butane and 5.2 parts by weight of perfluorohexane wereadded with vigorous stirring at 23° C to a mixture comprising

82 parts by weight of a polyoxypropylene-polyol having a hydroxyl numberof 400, prepared from sucrose as the initiator molecule and1,2-propylene oxide,

10 parts by weight of a polyoxypropylene glycol having a hydroxyl numberof 105, prepared using 1,2-propanediol as the initiator molecule,

2.5 parts by weight of a polysiloxane foam stabilizer (SR 321 from thePB Company),

2.0 parts by weight of N,N-dimethylcyclohexylamine and

3.6 parts by weight of water.

The resultant emulsion (component A) was mixed with the component Bdescribed in Example 1 in a weight ratio of 100:157 with vigorousstirring, and the reaction mixture was allowed to expand as described inExample 1.

A fine-filled rigid PU foam having a mean pore diameter of 273 μm and adensity of 32 g/l was obtained. The proportion of closed cells was 95%and the thermal conductivity was 18.6 mW/m K.

EXAMPLE 5

The procedure was similar to that of Example 4, but a blowing agentmixture comprising

4.15 parts by weight of vinylperfluoro-n-butane and

4.85 parts by weight of perfluoropentane was used.

The mixing ratio between components A and B was 100:157.

A fine-celled rigid PU foam having a mean pore diameter of 241 μm and adensity of 32 g/l was obtained. The proportion of closed cells was 94%and the thermal conductivity was 18.3 mW/m K.

EXAMPLE 6

The procedure was similar to that of Example 4, but a blowing agentmixture comprising 3.9 parts by weight of vinylperfluoro-n-butane and5.1 parts by weight of 1H-perfluorohexane was used.

The mixing ratio between components A and B was 100:157.

A fine-celled rigid PU foam having a mean pore diameter of 420 μm and adensity of 31 g/l was obtained. The proportion of closed cells was 93%and the thermal conductivity was 21 mW/m K.

EXAMPLE 7 Component A

To prepare the blowing agent-containing emulsion, 9.0 parts by weight ofvinylperfluoro-n-hexane were added with vigorous stirring at 23° C. to amixture comprising

91.3 parts by weight of a polyoxypropylene-polyol having an OH number of400, prepared from sucrose as the initiator molecule and 1,2-propyleneoxide,

2.5 parts by weight of foam stabilizer (VPAC 3408 from Bayer AG),

2.0 parts by weight of N,N-dimethylcyclohexylamine and 4.2 parts byweight of water.

The resultant emulsion (component A) was mixed with the component Bdescribed in Example 1 in a weight ratio of 100:153 with vigorousstirring, and the reaction mixture was allowed to expand as described inExample 1.

A fine-celled rigid PU foam having a density of 29 g/l and containing93% of closed cells was obtained. The thermal conductivity was 20.5 mW/mK.

EXAMPLE 8

The procedure was similar to that of Example 4, but a blowing agentmixture comprising

8.4 parts by weight of vinylperfluoro-n-butane and 4.6 parts by weightof 2,2,2-trifluoroethyl difluoromethyl ether was used.

The resultant emulsion (component A) was mixed with the component Bdescribed in Example 1 in a weight ratio of 100:157 with vigorousstirring, and the reaction mixture was allowed to expand as described inExample 1.

A fine-celled rigid PU foam having a density of 28.9 g/l was obtained.The proportion of closed cells was 88% and the thermal conductivity was19.5 mW/m K.

EXAMPLE 9 Component A

To prepare the blowing-agent-containing emulsion,

8.6 parts by weight of vinylperfluoro-n-hexane and 1.8 parts by weightof n-pentane

were added with vigorous stirring at 23° C. to 100 parts by weight of amixture comprising

91.9 parts by weight of a polyoxypropylene-polyol having an OH number of400, prepared from sucrose as the initiator molecule and 1,2-propyleneoxide,

2.0 parts by weight of N,N-dimethylcyclohexylamine,

3.6 parts by weight of water and

2.5 parts by weight of a foam stabilizer (VPAC 3408 from Bayer AG).

The resultant emulsion (component A) was mixed with the component Bdescribed in Example 1 in a weight ratio of 100:142 with vigorousstirring, and the reaction mixture was allowed to expand as described inExample 1.

A fine-celled rigid PU foam having a density of 31.6 g/l was obtained.The proportion of closed cells was 91% and the thermal conductivity was20.0 mW/m K.

EXAMPLE 10

The procedure was similar to that of Example 9, but a blowing agentmixture comprising

4.5 parts by weight of vinylperfluoro-n-butane and

4.5 parts by weight of oligomeric perfluoropropylene oxide (Galden® HT70 from Montedison) was used.

The resultant emulsion (component A) was mixed with the component Bdescribed in Example 1 in a weight ratio of 100:144 with vigorousstirring, and the reaction mixture was allowed to expand as described inExample 1.

A fine-celled rigid PU foam having a density of 34.2 g/l was obtained.The proportion of closed cells was 92% and the thermal conductivity was19.3 mW/m K.

EXAMPLE 11

The procedure was similar to that of Example 9, but a blowing agentmixture comprising 4.0 parts by weight of vinylperfluoro-n-butane and2.5 parts by weight of 1,1,1-trifluoro-2,2-dichloroethane was used.

The resultant emulsion (component A) was mixed with the component Bdescribed in Example 1 in a weight ratio of 100:148 with vigorousstirring, and the reaction mixture was allowed to expand as described inExample 1.

A fine-celled rigid PU foam having a density of 29.5 g/l was obtained.The proportion of closed cells was 90% and the thermal conductivity was19.8 mW/m K.

EXAMPLE 12

An emulsion of blowing agent is prepared by adding, with vigorousstirring, 10 parts by weight of vinylperfluoro-n-butane to a mixture of93 parts by weight of tripropylene glycol,

2 parts by weight of amine catalyst (Polycat® 8 from AbbottLaboratories),

1.5 parts by weight of silicone (Tagostab B 8409 from Goldschmidt AG.)and 3.5 parts by weight of water.

100 parts by weight of the emulsion thus obtained are reacted with 202parts by weight of a polyisocyanate (Lupranat M205 from BASF AG.)consisting of a mixture of diphenylmethane diisocyanate andpolyphenylpolymethylene polyisocyanate and having an NCO content of 31%by weight.

A rigid foam with a density of 34 g/l is obtained. The proportion ofclosed cells is 89% and this thermal conductivity of the foam is 21 mW/mK.

EXAMPLE 13

9 parts by weight of vinylperfluoroisopropane are stirred vigorouslywith a mixture of:

93 parts by weight of a polyoxypropylene polyol having a hydroxyl numberof 410, obtained by addition of 1,2-propylene oxide to sucrose

2 parts by weight of amine catalyst (Polycat® 8)

1 part by weight of silicone (Tegostab® B8409) and

3.5 parts by weight of water.

By reacting 100 parts by weight of the resultant emulsion with 157 partsby weight of the same polyisocyanate (Lupranat M208) as in Example 1, arigid foam is obtained with a density of 31 g/l and a thermalconductivity of 20 mW/m K.

EXAMPLE 14

An emulsion is obtained by stirring 7 parts by weight ofvinylperfluoro-n-hexane with a mixture of 91.9 parts by weight oftripropylene glycol,

2 parts by weight of N,N,N',N,-tetramethylhexamethylenediamine, 2.5parts by weight of a foam stabiliser (OS710 from Bayer AG) and

3.6 parts by weight of water.

By reacting 100 parts by weight of this emulsion with 181 parts byweight of the same polyisocyanate as in Example 1, a rigid foam withfine cells is obtained, which has a density of 34 g/l and a thermalconductivity of 19.5 mW/m K.

EXAMPLE 15

An emulsion is obtained by stirring 13.8 parts by weight ofvinylperfluoro-n-butane and 1.1 parts by weight of cyclopentane with amixture of

91.9 parts by weight of the same polyol as in Example 13,

2 parts by weight of Polycat® 8 catalyst, 2.5 parts by weight ofsilicone (Tegostab® B8406 from Goldschmidt AG) and

3.6 parts by weight of water.

By reacting 100 parts by weight of this emulsion with 150 parts byweight of the same polyisocyanate as in Example 1, a rigid foam withfine cells is obtained, with a density of 34 g/l. The proportion ofclosed cells is 94% and the thermal conductivity of the foam is 20.5mW/m K.

EXAMPLE 16

An emulsion of blowing agent is prepared by stirring 10.5 parts byweight of vinylperfluoro-n-butane and 5.7 parts by weight ofdifluoromethyl 2,2,2-trifluoroethyl ether into a mixture of

92.4 parts by weight of dipropylene glycol,

3.6 parts by weight of water, 1.5 parts by weight of Polycat® 8 catalystand

2.5 parts by weight of OS 710 stabiliser.

By reacting 100 parts by weight of the resultant emulsion with 227 partsby weight of the same polyisocyanate as in Example 1, a foam with finecells is obtained, which has a density of 33.6 g/l, a proportion ofcloned cells of 89% and a thermal conductivity of 19.9 mW/m K.

EXAMPLE 17

An emulsion of blowing agent is prepared by stirring 8 parts by weightof vinylperfluoro-n-butane and 11 parts by weight of perfluorohexaneinto a mixture of:

46.1 parts by weight of a polyoxypropylene polyol having a hydroxylnumber of 475 obtained by addition of 1,2-propylene oxide to sorbitol,

46 parts by weight of tripropylene glycol,

3.6 parts by weight of water,

1.8 parts by weight of Polycat® 8 and

2.5 parts by weight of stabiliser Tegostab® B 8406.

By reacting 100 parts by weight of this emulsion with 158 parts byweight of the same polyisocyanate as in Example 1, a foam with finecells is obtained, which has

We claim:
 1. A blowing agent-containing emulsion which containsat least one vinylfluoroalkane of the formula

    CH.sub.2 ═CH--C.sub.n F.sub.2n+1

in which n is an integer from 1 to 6, (di), and at least one organic and/or modified organic polyisocyanate (a) or at least one relatively high-molecular-weight compound containing at least two reactive hydrogen atoms (b), or at least one low-molecular-weight chain extender and/or crosslinking agent (c), or a mixture of (b) and (c).
 2. A blowing agent-containing emulsion which comprisesfrom 1 to 40 parts by weight, based on 100 parts by weight of (b) or (b) and (c), of one or more vinylfluoroalkanes of the formula CH₂ ═CH--C_(n) F_(2n+1) in which n is an integer from 1 to 6, (di), from 0 to 5 parts by weight, based on 100 parts by weight of (b) or (b) and (c), of water, (dii), from 0 to 36 parts by weight, based on 100 parts by weight of (b) or (b) and (c), of at least one further, low-boiling, physical blowing agent (dii) which is different from (di) and is only sparingly soluble or insoluble in the starting components (a), (b) and (c), and at least one relatively high-molecular-weight compound containing at least two reactive hydrogen atoms (b), or a mixture of (b) and a low-molecular-weight chain extender and/or crosslinking agent (c).
 3. A blowing agent-containing emulsion which comprisesfrom 1 to 40 parts by weight, based on 100 parts by weight of (b) or (b) and (c), of one or more vinylfluoroalkanes of the formula CH₂ ═C_(n) F_(2n+1) in which n is an integer from 1 to 6, (di), from 0 to 5 parts by weight, based on 100 parts by weight of (b) or (b) and (c), of water, (dii), from 0 to 36 parts by weight, based on 100 parts by weight of (b) or (b) and (c), of at least one low-boiling, fluorinated or perfluorinated organic compound which is only sparingly soluble or insoluble in the starting components (a), (b) and (c), and contains no bonded olefinically unsaturated groups in the molecule, (dii), and at least one relatively high-molecular-weight compound containing at least two reactive hydrogen atoms (b), or a mixture of (b) and a low-molecular-weight chain extender and/or crosslinking agent (c). 